1. Field of the Invention
The invention relates generally to a target source for thin film sputter deposition, and more particularly to an ion beam deposition target source having an interlocking interface and a replaceable inner central insert.
2. Description of the Prior Art
Sputter deposition processes that use ion beam target sources are found in a variety of applications. Sputter deposition is one of several well known techniques for applying or depositing a thin layer on a substrate. In ion beam bombardment sputtering, a high energy source of ions is directed toward a target source. The force of the bombardment of ions imparts sufficient energy to the atoms of the target source to cause the energized atoms to leave the target source, form a particle flux, and deposit a thin film on a substrate. The advantages of using ion beam sputter deposition include isolation of the substrate from energetic electron bombardment and independent control over the ion energy and current density striking the target. The basic techniques of ion beam sputter deposition are well known in the art.
Generally, any target source material that can be physically placed in a vacuum chamber can be sputtered by ion beam deposition. This includes materials comprised of a single chemical element, alloys, composites, and compounds. In depositing a thin film of a given chemical composition, where the target source is relied on as a primary source of deposition material, the target source can be prepared by vacuum, inert, or open atmosphere melting. The material is melted by induction, resistive, electric arc, or similar melting methods. The material is subsequently formed into an appropriate shape through known material processing methods. Alternatively, the material may be formed by a number of powder consolidation methods such as press and sinter, hot isostatic pressing, uniaxial hot pressing or similar well-known techniques. These methods can be designed to produce material of a high purity and structural integrity. Deposition targets are typically attached to a backing holder or plate by a bonding layer for accurate placement in the vacuum chamber. The bonding layer usually comprises solder. U.S. Pat. No. 4,430,190 to Eilers et al. discloses an example of a deposition target source bonded to a backing holder or plate.
Other factors that can affect the rate and extent of erosion of a deposition target source include the intensity, direction and size of the ion beam used in the sputtering process. However, because the diameter of the ion beam is generally smaller than the dimensions of the deposition target source used, excessive erosion typically occurs on the region of the target source that is directly impacted by the ion beam (typically the center region), while the region of the target source not hit by the ion beam (typically the outer region) demonstrates little to no erosion. Thus, the eroded region will generally correspond to the dimensions of the ion beam bombarding the region.
In part because of the very high costs of many deposition materials, such as tantalum and precious metals, there is currently a need for producing ion beam deposition target sources that are significantly lower in cost. We have solved this and related problems by producing ion beam deposition target sources that have a replaceable insert which is centrally located to correspond to the region eroded by the ion beam. By developing a deposition target source having a replaceable insert, the region of the target source not eroded by the ion beam can remain in place attached to the holder or frame supporting the target. The ability to remove and replace only the insert portion of the deposition target source eroded by the ion beam saves time and has economic benefits such as reducing the costs associated with materials used to make the target, reducing the costs associated with processing and machining the target source, and permitting the reuse of the remainder of the target not eroded, rather than replacing the entire target source as is currently done.
With the present invention, the replaceable central inner insert can be removed from the vacuum chamber and replaced once eroded, while allowing the outer uneroded portion of the target source to remain attached to a backing holder or plate. Alternatively, if the entire target source and backing plate are returned to a central processing center, both the insert and the outer portion can be removed from the backing plate for inspection by melting or dissolving the bonding layer, and the same outer portion together with a new central insert attached to the backing plate by a fresh bonding layer.
Accordingly, it is a principal object of this invention to provide an ion beam deposition target source having a centrally located inner insert that can be removed and replaced when eroded, wherein the outer region of the target source not eroded by the ion beam can either remain in place attached to a backing plate located on an ion beam deposition (IBD) machine or be reused with a new central insert if the target source is to be removed for more efficient recycling. The deposition target source of the present invention comprises at least a centrally located removable inner insert completely surrounded by an outer region. The inner insert and the outer region are joined to each other to form the deposition target source by an interlocking interface to prevent contaminants, such as atoms from the bonding layer, from also being formed in the particle flux. The deposition target source is attached by the bonding layer to a conventional backing plate located on an IBD machine. The bonding layer preferably comprises solder.
It is another object of this invention to provide an ion beam deposition target source having a geometric shape including, but not limited to, round, rectangular or oval shapes.
It is a further object of this invention to provide a reusable ion beam deposition target source wherein the outer region of the target source not eroded by the ion beam remains attached to the backing plate on an IBD machine, and/or can be reused rather than replaced along with the eroded inner insert.
It is an additional object of this invention to provide an ion beam deposition target source that requires less replacement materials because only the eroded inner insert is replaced, rather than the entire target source.
It is another object of this invention to provide an ion beam deposition target source that reduces the costs and time associated with the processing and machining of a replacement target source because only the eroded inner insert is replaced, rather than the entire target source.